Brown Recluse Spider

HYG-2061-04

The brown recluse spider is uncommon in Ohio. Nonetheless, OSU Extension
receives numerous spider specimens that homeowners mistakenly suspect to be the
brown recluse. Media attention and public fear contribute to these misdiagnoses.

The brown recluse belongs to a group of spiders that is officially known as
the "recluse spiders" in the genus Loxosceles (pronounced
lox-sos-a-leez). These spiders are also commonly referred to as "fiddleback"
spiders or "violin" spiders because of the violin-shaped marking on the top
surface of the cephalothorax (fused head and thorax). However, this feature can
be very faint depending on the species of recluse spider, particularly those in
the southwestern U.S., or how recently the spider has molted.

The common name, brown recluse spider, pertains to only one species,
Loxosceles reclusa. The name refers to its color and habits. It is a
reclusive creature that seeks and prefers seclusion.

Distribution

The brown recluse spider and ten additional species of Loxosceles are
native to the United States. In addition, a few non-native species have become
established in limited areas of the country. The brown recluse spider is found
mainly in the central Midwestern states southward to the Gulf of Mexico (see
map). Isolated cases in Ohio are likely attributable to this spider occasionally
being transported in materials from other states. Although uncommon, there are
more confirmed reports of Loxosceles rufescens (Mediterranean recluse)
than the brown recluse in Ohio. It, too, is a human-associated species with
similar habits and probably similar venom risks (unverified).

Identification

not actual size

Recluse spiders have six eyes that are arranged in
pairs.

In the mature brown recluse spider as well as some other species of recluse
spiders, the dark violin marking is well defined, with the neck of the violin
pointing toward the bulbous abdomen. The abdomen is uniformly colored, although
the coloration can range from light tan to dark brown, and is covered with
numerous fine hairs that provide a velvety appearance. The long, thin, brown
legs also are covered with fine hairs, but not spines. Adult brown recluse
spiders have a leg span about the size of a quarter. Their body is about 3/8
inches long and about 3/16 inches wide. Males are slightly smaller in body
length than females, but males have proportionally longer legs. Both sexes are
venomous. The immature stages closely resemble the adults except for size and a
slightly lighter color. Whereas most spiders have eight eyes, recluse spiders
have six eyes that are arranged in pairs in a semicircle on the forepart of the
cephalothorax (see close-up view). A 10X hand lens or microscope is needed to
see this diagnostic feature. In order to determine the exact species of
Loxosceles, the spider's genitalia need to be examined under a high-power
microscope. This requires the skills of a spider expert.

Life Cycle and Habits

Egg laying primarily occurs from May through July. The female lays about 50
eggs that are encased in an off-white silken sac that is about 2/3-inch
diameter. Each female may produce several egg sacs over a period of several
months. Spiderlings emerge from the egg sac in about a month or less. Their
development is slow and is influenced by weather conditions and food
availability. It takes an average of one year to reach the adult stage from time
of egg deposit. Adult brown recluse spiders often live about one to two years.
They can survive long periods of time (about 6 months) without food or water.

The brown recluse spider spins a loose, irregular web of very sticky,
off-white to grayish threads. This web serves as the spider's daytime retreat,
and it often is constructed in an undisturbed corner. This spider roams at night
searching for insect prey. Recent research at the University of Kansas indicates
that the brown recluse spider is largely a scavenger, preferring dead insects.
Mature males also roam in search of females.

Brown recluse spiders generally occupy dark, undisturbed sites, and they can
occur indoors or outdoors. In favorable habitats, their populations are usually
dense. They thrive in human-altered environments. Indoors, they may be found in
attics, basements, crawl spaces, cellars, closets, and ductwork or registers.
They may seek shelter in storage boxes, shoes, clothing, folded linens, and
behind furniture. They also may be found in outbuildings such as barns, storage
sheds, and garages. Outdoors, brown recluse spiders may be found underneath
logs, loose stones in rock piles, and stacks of lumber.

The brown recluse spider is not aggressive, and it normally bites only when
crushed, handled or disturbed. Some people have been bitten in bed after
inadvertently rolling over onto the spider. Others have been bitten after
accidentally touching the spider when cleaning storage areas. Some bites occur
when people put on seldom used clothing or shoes inhabited by a brown recluse.

Bite Symptoms

The physical reaction to a brown recluse spider bite depends on the amount of
venom injected and an individual's sensitivity to it. Some people are unaffected
by a bite, whereas others experience immediate or delayed effects as the venom
kills the tissues (necrosis) at the site of the bite. Many brown recluse bites
cause just a little red mark that heals without event. The vast majority of
brown recluse bites heal without severe scarring (http://spiders.ucr.edu/avoidbites.html).

Initially, the bite may feel like a pinprick or go unnoticed. Some may not be
aware of the bite for 2 to 8 hours. Others feel a stinging sensation followed by
intense pain. Infrequently, some victims experience general systemic reactions
that may include restlessness, generalized itching, fever, chills, nausea,
vomiting, or shock. A small white blister usually initially rises at the bite
site surrounded by a swollen area. The affected area enlarges and becomes red,
and the tissue is hard to the touch for some time. The lesion from a brown
recluse spider bite is a dry, blue-gray or blue-white, irregular sinking patch
with ragged edges and surrounding redness--termed the "red, white, and blue
sign." The lesion usually is 1½ inches by 2¾ inches or smaller. Characteristics
of a bite are further discussed at
http://www.amednews.com/free/hlsa0805.

The bite of the brown recluse spider can result in a painful, deep wound that
takes a long time to heal. Fatalities are extremely rare, but bites are most
dangerous to young children, the elderly, and those in poor physical condition.
When there is a severe reaction to the bite, the site can erupt into a "volcano
lesion" (a hole in the flesh due to damaged, gangrenous tissue). The open wound
may range from the size of an adult's thumbnail to the span of a hand. The dead
tissue gradually sloughs away, exposing underlying tissues. The sunken,
ulcerating sore may heal slowly up to 6 to 8 weeks. Full recovery may take
several months and scarring may remain.

It is difficult for a physician to accurately diagnose a "brown recluse bite"
based simply on wound characteristics. It is absolutely necessary to have the
spider for a positive identification. Necrotic wounds can result from a variety
of agents such as bacteria (Staphylococcus, "flesh-eating" Streptococcus, etc.),
viruses, fungi, and arthropods (non-recluse spiders, centipedes, mites, ticks,
wasps, bedbugs, kissing bugs, biting flies, etc.). Necrotic conditions also can
be caused by vascular and lymphatic disorders, drug reactions, underlying
diseases states, and a variety of other agents. An annotated list of conditions
that could be mistaken for a brown recluse spider bite is available at
http://www.ama-assn.org/amednews/2002/08/05/hlsa0805.htm. Misdiagnosis of
lesions as brown recluse bites can delay appropriate care.

First Aid

If bitten, remain calm, and immediately seek medical attention (contact your
physician, hospital and/or poison control center). Apply an ice pack directly to
the bite area to relieve swelling and pain. Collect the spider (even a mangled
specimen has diagnostic value), if possible, for positive identification by a
spider expert. A plastic bag, small jar, or pill vial is useful and no
preservative is necessary, but rubbing alcohol helps to preserve the spider.

An effective commercial antivenin is not available. The surgical removal of
tissue was once standard procedure, but now this is thought to slow down wound
healing. Some physicians administer high doses of cortisone-type hormones to
combat hemolysis and other systemic complications. Treatment with oral dapsone
(an antibiotic used mainly for leprosy) has been suggested to reduce the degree
of tissue damage. However, an effective therapy has not yet been found in
controlled studies.

Control

Control of indoor infestations of the brown recluse spider can take a long
time (6 months or more) and can be difficult because humans have a very low
tolerance for this pest, it tends to be widely dispersed within infested
buildings, and it seeks secluded sites. Control of spiders, including the brown
recluse, is best achieved by following an integrated pest management (IPM)
approach. IPM involves using multiple approaches such as preventive measures,
exclusion, sanitation, trapping, and chemical treatment when necessary.

Preventing spider bites

Shake out clothing and shoes before getting dressed.

Inspect bedding and towels before use.

Wear gloves when handling firewood, lumber, and rocks (be sure to
inspect the gloves for spiders before putting them on).

Remove bedskirts and storage boxes from underneath beds. Move the bed
away from the wall.

Exercise care when handling cardboard boxes (recluse spiders often are
found in the space under folded cardboard flaps).

Non-chemical control

Dust and vacuum thoroughly to remove spiders, webs, and egg sacs
(dispose of the vacuum bag in a container outdoors).

Use a rolled up newspaper or fly swatter to kill individual spiders.

Insecticides

There are many labeled pesticides for spider control. Some are labeled for
homeowner use, while others are labeled only for the licensed, certified
pesticide applicator. It would be prudent to enlist the services of a
professional pest management company when dealing with an indoor infestation of
the brown recluse spider.

Research indicates that recently developed pyrethroids (e.g., cyfluthrin,
cypermethrin, etc.) are particularly effective against brown recluse spiders.
Wettable powders and microencapsuled "slow-release" formulations of these
chemicals provide residual activity and are preferable to using emulsion-type
sprays. Insecticide treatments should be applied so that the chemical contacts
as many spiders and webs as possible. Residual liquid sprays should be applied
to the outside perimeter of the home (including under eaves, patios, and decks;
behind window shutters), baseboards, undisturbed corners, and other suspected
spider harborages. Residual dusts should be applied to voids and inaccessible
areas where spiders may hide. Aerosol flushing agents such as pyrethrins, though
ineffective by themselves in providing control, can cause spiders to move about
so that they contact treated surfaces.

Any opinions, findings, conclusions, or recommendations
expressed in this publication are those of the author(s) and do not
necessarily reflect the view of the U.S. Department of Agriculture

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